Speciation is a process by which separate populations evolve a restricted capacity to reproduce and exchange genes with each other. When this "reproductive isolation" is complete, these populations have become new species that will henceforth experience genetically independent evolutionary histories. Recently, there has been increasing interest in how speciation might be promoted by the divergent adaptation of populations to different ecological challenges. It has been suggested, for example, that a tendency to ecologically specialize may help explain why about one quarter of all species of organisms on Earth are plant-feeding insects. Indeed, most species of insect herbivores are ecological specialists that use only a few kinds of host plants. Many of these insects are intimately adapted to their host plant, which represents their home, their food, and the place where they mate and reproduce.
In my research, I take a multidisciplinary approach in studying ecological specialization and the ways in which it might promote speciation in plant-feeding insects. My research includes experimental studies of insect feeding and mating behaviors in response to various plant taxa, as well as molecular studies of the population genetic mechanisms and phylogenetic patterns exhibited by host-associated herbivore species. By combining these approaches, I investigate both the ecological causes and the evolutionary consequences of host plant specialization and insect speciation. Since my work has an important geographic component, I spend part of each summer travelling and collecting insects across North America, where my study organisms live. My current study systems, a genus of leaf beetles and a species of aphid, are both amenable to rearing and study in the greenhouse and laboratory. They provide two quite biological distinctive and distantly related herbivore taxa for my investigations.